a(n) = 100*n^2 + 100*n + 21.

Terms

a(0) =21a(1) =221a(2) =621a(3) =1221a(4) =2021a(5) =3021a(6) =4221a(7) =5621a(8) =7221a(9) =9021a(10) =11021a(11) =13221a(12) =15621a(13) =18221a(14) =21021a(15) =24021a(16) =27221a(17) =30621a(18) =34221a(19) =38021a(20) =42021a(21) =46221a(22) =50621a(23) =55221a(24) =60021a(25) =65021a(26) =70221a(27) =75621a(28) =81221a(29) =87021